Battery powered surgical handpieces have been commercially available for some time and have been found convenient by surgeons for reasons including the lack of a trailing power cord. A typical handpiece has a pistol shaped housing including a barrel and depending handle, a trigger at the juncture of the handle and barrel for turning on and off and setting the speed of an internal motor, and a tool carrier or chuck at the front end of the barrel. Typically, a housing incorporates the handle and barrel and contains a removable, rechargeable battery, a motor and a drive train connecting the motor and tool carrier. Handpieces of this general kind have been equipped as rotary drills, reamers, wire drivers, and saws of sagittal, oscillating and reciprocating type, for example.
Battery operated surgical handpieces of this kind have been marketed by the assignee of the present invention, Stryker Corporation of Kalamazoo, Mich., including for example the model No. 2102. In these, the housing has been formed of a gracefully contoured sheet metal envelope of pistol contour, typically a stainless steel envelope, sized to comfortably fit the hand of the user. By locating the motor and speed reduction gearing in the handle, to drive through angled gearing the output shaft extending forward in the barrel, and inserting the rechargeable battery pack removably into the open rear end of the barrel, and providing a hole axially through the battery pack in coaxial alignment with a suitable through hole in the output shaft, it has been possible to provide a wire driver type surgical handpiece, namely one in which a wire inserted through the rear end of the barrel is fed out the forward end of the barrel to a surgical site as part of a drilling operation for example.
A further example of battery powered surgical hand-pieces of this general kind is disclosed in Mongeon et al U.S. Pat. No. 4,728,876. Same comprises a housing having a barrel of circular cross section and a detachable handle releasably dependent therefrom. The trigger is mounted pendently from the barrel and is thus separable from the handle. The handle carries a rechargeable battery and switch means actuable by the trigger, being coupled thereto in a releasable manner to permit ready removal of the handle in a manner to allow charging/replacement of the battery handle. Rearward sliding of the handle with respect to the barrel achieves release. A cylindrical rear portion of the barrel is rotatable about the central axis of the barrel to achieve forward/off/reverse control of the motor and houses the brushes and commutator portion of the motor. Extending forward along the barrel are the motor, a two-speed shiftable gear reduction set, and an output shaft for driving a tool carrier.
The present invention arose from a continuing effort to improve battery powered surgical handpieces of the general kind exemplified above.
Accordingly, embodiments of the present invention are respectively intended to fulfill one or more of the following objects and purposes. A battery powered surgical handpiece is well balanced and has a contoured rigid sheet metal housing fitted to the human hand to maximize comfort and controllability in surgical procedures of substantial duration. A motor control circuit, motor, speed reduction gearing, output shaft and tool carrier can be preassembled in a cartridge and test run prior to insertion in the housing barrel, so that if any part of such cartridge is defective, it will be discovered and can be cured prior to completing assembly of the handpiece. The motor, drive train and output shaft are precisely coaxially located in a precisely configured, circular cross section cartridge casing, which in turn is fixedly though removably located in the formed sheet metal barrel, so as to avoid the substantial difficulty (if not impossibility) of forming the sheet metal barrel as precisely as needed for proper location of the motor and speed reduction unit and output shaft with respect to each other while permitting the above-mentioned comfortable fitting of the housing, including the barrel, to the human hand. The exteriors of the motor, speed reduction unit and output shaft need not be individually sealed, fitted or fixed to the inner surface of the sheet metal housing, and the barrel and handle can be of non-circular cross section. Adequate room is provided for a powerful motor without need for a handle cross section which is too large or improperly shaped for maximum use or comfort and control. The motor is of brushless type having a permanent magnet rotor. The electronic circuitry for controlling the brushless DC motor, in response to trigger and reversing switch actuation, is contained in the rear portion of the barrel immediately behind the brushless DC motor. A central passage opens through the front and rear ends of the barrel and extends through the electronic control unit in coaxial relation with corresponding central passages through the motor, speed reduction unit and output shaft, to enable use of the handpiece as a wire driver. Seals prevent foreign material and moisture (e.g. steam in a sterilizing autoclave) in the central passage from entering into the interior of the housing and into components within the housing and outside of such central passage. Adjacent the rear of the motor, a rear seal is disposed between fixed and rotating parts of the drive train but is not required to engage the relatively high speed motor shaft, so as to substantially extend the expected operating life of such seal and minimize power loss in the seals. The output shaft has a heavy duty forward portion capable of transmitting substantial torque to a tool carrier and a much lighter duty rear portion extending loosely through and rearward of the motor for rotatably engaging a rear seal, the heavy front and light rear portions of the output shaft being rigidly fixed to and sealed with respect to each other, the two parts of the output shaft being hollow and telescoped and yet sealed at their joinder to prevent ingress of moisture into the barrel of the handpiece. The trigger actuates a variable speed control and a separate on/off switch structure so that actuating movement of the trigger first must close the switch contacts to their "on" position, prior to raising the speed to control portion of the trigger unit above a zero speed setting. Use of a brushless permanent magnet motor eliminates reliability and maintenance problems associated with brushes and provides greater operating efficiency of the motor thereby allowing greater run time for a given battery capacity, and thereby permitting a reduction in battery size for a given run time, to reduce the weight and bulk of the handpiece. The upper portion and major length of the handle connects rigidly and permanently and indeed integrally with the barrel of the handpiece housing to provide a rigid, long lasting handpiece exterior not readily damaged and particularly wherein the handle cannot come loose from the barrel in use. The trigger is mounted on this fixed portion of the handle. From the bottom portion of the handle protrudes a minor portion of a rigid battery which has a major upper portion insertable upward into the open bottom of the handle, such that the exposed part of the battery acts simply as a downward extension of the handle, thereby not interfering with the fit of the hand of the user to the handpiece or with the balance of the hand-piece, and permitting use of battery packs of greater length where greater battery capacity is needed, and allowing substantial overlap of the battery telescoped within the handle for rigidity of mounting of the battery pack with respect to the handle, and providing more than adequate space for latching and electrical contact of the battery pack with respect to the rest of the handpiece. The substantially telescoped overlap of the battery pack and a latch mechanism within the hollow bottom portion of the handle substantially eliminates any tendency for handpiece vibration or careless handling to loosen or break the battery pack/handpiece connection.
Further objects and purposes of the invention will be apparent to persons acquainted with apparatus of this type upon reading the following description and inspecting the accompanying drawings.